# std::set<Key,Compare,Allocator>::empty

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< cpp‎ | container‎ | set

bool empty() const; |  | (noexcept since C++11)

Checks if the container has no elements, i.e. whether begin() == end().

### Parameters

(none)

### Return value

true if the container is empty, false otherwise.

### Complexity

Constant.

### Example

The following code uses `empty` to check if a std::set<int> contains any elements:

Run this code

    #include <iostream>
    #include <set>

    int main()
    {
        std::set<int> numbers;
        std::cout << std::boolalpha;
        std::cout << "Initially, numbers.empty(): " << numbers.empty() << '\n';

        numbers.insert(42);
        numbers.insert(19937);
        std::cout << "After adding elements, numbers.empty(): " << numbers.empty() << '\n';
    }

Output:

    Initially, numbers.empty(): true
    After adding elements, numbers.empty(): false

### See also

size | returns the number of elements (public member function)
empty (C++17) | checks whether the container is empty (function template)

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